Chemistry 2001 JAMB Past Questions - Question 17: Pure solvents are obtained by

Correct Answer

A

Explanation

 Pure solvents can be obtained through various methods, typically involving processes that remove impurities and contaminants. Here are some common methods for obtaining pure solvents:

1. **Distillation:** Distillation is a widely used method for purifying solvents. It involves heating the solvent to its boiling point and then condensing the vapor back into a liquid. This process effectively separates the solvent from impurities, as the boiling points of different substances are usually distinct.

2. **Fractional Distillation:** Similar to distillation, fractional distillation is used when there are multiple components in a mixture with close boiling points. It allows for more precise separation of different components based on their boiling points.

3. **Rectification:** This is a process similar to distillation that involves repeated vaporization and condensation to enhance the separation of components in a mixture.

4. **Solvent Extraction:** In this method, a solvent is used to selectively dissolve and remove impurities from the desired solvent. After extraction, the solvent is typically evaporated to leave behind the purified substance.

5. **Chromatography:** Various chromatographic techniques, such as column chromatography or high-performance liquid chromatography (HPLC), can be used to separate and purify solvents based on differences in their chemical properties.

6. **Membrane Filtration:** Membrane filters with specific pore sizes can be used to remove particulate matter and impurities from solvents.

7. **Drying Agents:** Some solvents may contain water or moisture, which can be removed by using drying agents such as molecular sieves or desiccants. These agents selectively absorb water and leave the solvent dry.

8. **Crystallization:** For certain solvents, crystallization can be employed to purify them. The solvent is cooled, and the purified component crystallizes out, leaving impurities in the solution.

The choice of method depends on the specific characteristics of the solvent and the impurities present. It's common to use a combination of these techniques to achieve a high level of purity. Additionally, the purity of solvents is often expressed in terms of their grade, such as analytical grade or high-performance liquid chromatography (HPLC) grade, indicating the level of purity achieved through these methods.